The present invention relates to a method for opening a movable cowl actuated by an electric motor and fitted to a thrust reverser for a turbojet.
The role of a thrust inverter for the landing of an aircraft is to improve the braking capacity of an aircraft by redirecting at least a portion of the thrust generated by the turbojet toward the front. In this phase, the inverter obstructs the gas exhaust duct and directs the exhaust stream from the engine toward the front of the pod, thereby generating a counter-thrust which is added to the braking of the aircraft wheels.
The implementation means for achieving this reorientation of the stream vary depending on the type of reverser. However, in all cases, the structure of a reverser comprises movable cowls that can be moved between, on the one hand, a deployed position in which they open in the pod a passageway designed for the diverted stream, and, on the other hand, a retracted position in which they close this passageway. These movable cowls may also fulfill the function of diversion or simply activation of other diversion means.
In reversers with grilles, for example, the movable cowls slide along rails so that, by moving backwards during the opening phase, they reveal diversion blade grilles placed in the thickness of the pod. A system of link rods connects this movable cowl to blocking doors which deploy inside the exhaust channel and block the direct stream outlet. In reversers with doors, on the other hand, each movable cowl pivots in order to come and block the stream and divert it and is therefore active in this reorientation.
In a general manner, these movable cowls are actuated by hydraulic or pneumatic cylinders which require a network for the conveyance of a pressurized fluid. This pressurized fluid is conventionally obtained by tapping air from the turbojet in the case of a pneumatic system or by offtaking from the hydraulic circuit of the aircraft. However, such systems require considerable maintenance because the slightest leak in the hydraulic or pneumatic network may have damaging consequences both for the reverser and for the other parts of the pod. Furthermore, because of the reduced space available in the front frame of the reverser, the installation and protection of such a circuit are particularly awkward and bulky.
To alleviate the various disadvantages associated with pneumatic and hydraulic systems, thrust reverser manufacturers have sought to replace them and as much as possible fit their reversers with electromechanical actuators that are lighter and more reliable. Such a reverser is described in document EP 0 843 089.
It should be noted that, to close the reverser, the movable cowl is immobilized by locks. These locks are important components for in-flight safety and are part of the most sensitive components of the thrust reverser. The latter are therefore particularly susceptible to being damaged, or even broken, in the event of too great an impact of the movable cowl. Specifically, if, during the maneuver, the locks could not open, due to a blockage, the movable cowl in motion would come to collide with them with full force.
In order to prevent such an accident, the locks are dimensioned to be able to withstand the probable impacts, thereby increasing their weight, which is not desirable in aviation.